Problem: log messages in `oauth.lua`, `gcal.lua`, `gtasks.lua`, and
`s3.lua` were inconsistent — some lacked a backend prefix, others used
sentence-case or bare error strings without identifying the source.
Solution: prefix all user-facing log messages with their backend name
(`gcal:`, `gtasks:`, `S3:`, `Google:`). Capitalize `S3` and `Google`
display names. Normalize casing and separator style (em dash) across
all sync log sites.
Barrett Ruth
422f8f9b05